The present invention pertains to a roller cutter assembly for rock boring machines. Rock boring machines have a plurality of these cutter assemblies mounted on a rotatable cutterhead. Conventionally, each cutter assembly includes a shaft which is adapted to be secured to the cutterhead, a hub mounted on bearings for rotation relative to the shaft and the cutterhead, and a cutter ring containing a plurality of cutter elements and being fixedly secured to the hub. The rock breaking elements on the cutter ring can either be a plurality of ring mounted button cutters peripherally mounted on the cutter ring, or the cutter ring itself can be a so-called disc cutter with a peripheral cutting edge. These cutter element arrangements are generically termable cutter ring means.
The hardness of the rock being bored dictates the cutter ring mean spacing, or kerf spacing, required for rock breaking at maximum energy efficiency and cutter survivability. Therefore it is desirable to be able to adjust kerf spacing conveniently. The kerf spacing on a cutterhead is traditionally not constant on the surface thereof.
If the kerf spacing is constant throughout the surface of a cutterhead, the cutters toward the periphery experience higher loads. Hence, the kerf spacing is reduced in positions toward the cutterhead periphery to equalize the cutter loads. When double cutter ring assemblies are substituted for single ring cutter assemblies (to reduce the overall kerf spacing on the cutterhead) the kerf spacing toward the periphery, on the double row cutter ring assemblies must again be decreased to equalize edge loading. Because, until now, the cutter spacing on any given two ring cutter assembly was not adjustable, an assortment of two ring cutter assemblies with progressively decreasing cutter spacing was required to equalize edge loading. There is obviously additional expense associated with maintaining an inventory of a plurality of groups of two ring cutter assemblies each having different cutter key spacing.
A dual ring cutter assembly sold by AB Sandvik Rock Tools of Sweden provides a limited form of variable cutter spacing by allowing the entire cutter assembly to be rotated from a first to a second, reverse, orientation on the cutterhead. However, the two rows of cutter rings on the Sandvik cutter assembly are not adjustable, and thus cutter ring spacing in this type of cutter assembly is not variable based on reorientation of one of the cutter rings with respect to the other. The Sandvik dual ring cutter assembly thus provides a very limited way of adjusting cutter kerf spacing.
Also known in the art is a dual ring disc cutter sold by Wirth of Germany. Neither the cutter assembly itself, nor the two cutter rings thereon are adjustable in any manner.
U.S. Pat. No. 4,793,427 issued to Lambson et al.; U.S. Pat. No. 3,981,370 issued to Bingham et al.; and U.S. Pat. No. 3,766,998 issued to Bower, Jr. all disclose disc cutters with removable cutter rings. U.S. Pat. No. 3,791,465 issued to Metge; U.S. Pat. No. 3,786,879 issued to Murdoc; U.S. Pat. No. 3,596,724 issued to Beechem; and U.S. Pat. No. 2,223,864 issued to Zublin all generally disclose roller cutters known in the art. U.S. Pat. No. 4,722,405 issued to Langford, Jr.; U.S. Pat. No. 4,452,325 issued to Radd et al.; U.S. Pat. No. 4,359,335 issued to Garner; and U.S. Pat. No. 4,339,009 issued to Busby all pertain to button cutter elements for cutter assemblies. However, none of the above patents discloses a cutter assembly having adjustable cutter spacing based on axial alteration of the orientation of the cutters on the cutter assembly.
A need thus exists for a cutter assembly in which cutter spacing is adjustable by axial alteration of the location of the cutter elements on the cutter assembly.
A need also exists for a cutter assembly in which alteration of the location of the cutter elements on the cutter assembly is accomplished by changing the relative direction that one cutter ring is oriented with respect to another cutter ring on the cutter assembly.
A need also exists for a cutter assembly in which the location of the cutter elements on the cutter assembly is altered by varying the number of spacers which brace the cutter rings to the cutter assembly.
A need also exists for a cutter assembly in which the location of the cutter elements on the cutter assembly is altered by changing the relative widths of the spacers employed to brace the cutter rings to the cutter assembly.